Problem in applying Vlookup using Openpyxl in Python

I have four worksheets within the same Workbook. Each of four sheets is shown below:

1. General Assumption Sheet

2. Ref Tariff Sheet

3. Plant Parameter Sheet

4. Indexed Tariff Sheet (need to populate this with Vlookups and Hlookups)

I have been trying to use both Vlookup and Hlookup in Python to match the plant name and year to get the desired value but I am getting errors.

To populate the Indexed Tariff Sheet, I need to match the Plant name in it with:

1. the same plant name e.g. Engro_PWR which has a value of 0.0501, in Ref Tariff Sheet. Then,

2. Multiply that value ( i.e. 0.0501) with the US CPI(in General Assumption Sheet) / US CPI (Plant Parameter Sheet) after matching both the years and plant names.

For example if the year is 2022 and Plant is Engro_PWR , then it becomes 0.0501*(269.73/216.74)

I am using Openpyxl only at the moment.

Any help would be very appreciated.

Code:

current_year=indexed_tariff['C1'].value
column_cell = 3

i='Engro_PWR'
if indexed_tariff['C1'].value <= 2027 and indexed_tariff['C1'].value > 1997:
    vlookup=pd.merge(data_FuelCost,to_dframe[['Fuel Price (Ref Values-Yearly)','Fuel Cost (Reference)']], on='Fuel Price (Ref Values-Yearly)',how='left')
    
    indexed_tariff[column_cell+str(row+5)] = str(i)

data_FuelCost is Ref Tariff Sheet

Error:

KeyError: "['Fuel Cost (Reference)'] not in index"